The present invention relates generally to diagnostic imaging and, more particularly, to an imaging tool that induces harmonic excitation within an object. Accordingly, the present invention is particularly applicable to elastography.
Increasingly, there has been a desire to image the elastic properties of tissue either through ultrasound or magnetic resonance imaging or other imaging techniques. Specifically, elastography has been identified as an effective tool in identifying malignant tumors within an object. That is, it is well known that malignant tumors are stiffer relative to their surrounding tissue when such tumors reach a requisite size. As such, by gathering information about the elastic properties of tissue, either through elastic field parameters, e.g., mechanical strain, or from elastic material parameters, e.g., Young's modulus, malignant tumors may be readily identified.
To perform such an elastography, it is necessary to apply a mechanical force to the object under investigation and measure the resulting mechanical displacement or strain field, from which other parameters may be determined. As referenced above, the observation of displacement is typically carried out either by ultrasound or another imaging technique, such as magnetic resonance (MR) imaging.
The drawback of current techniques of elastography lies in the poor signal-to-noise ratio of the displacement measurements, especially in case of freehand approaches. Accordingly, it is desirable to apply a harmonic mechanical excitation to the object, so that the resulting displacements will have a harmonic character. However, it is desirable for such a solution to fall within other desirable constraints; namely, excitation to an object in the range of 1-600 Hz as well as incorporation in a handheld tool for ultrasound or a tool that is RF-compatible for MR imaging.